there exists a chance, however small, that they can become productive members of society.
By killing a different productive member of society, they now have the debt of 2+ people to produce for instead of just themselves. The chance of a violent criminal or someone with a successful insanity defense ever reaching that productive is so small that its basically zero and shouldn't be considered in any thought.
Even if you worked them like a slave for the rest of their life, they cannot make up for the damage they've caused and should be treated as such.
By killing a different productive member of society, they now have the debt of 2+ people to produce for instead of just themselves. The chance of a violent criminal or someone with a successful insanity defense ever reaching that productive is so small that its basically zero and shouldn't be considered in any thought.
Even if you worked them like a slave for the rest of their life, they cannot make up for the damage they've caused and should be treated as such.